Project Summary/Abstract Adults with low socioeconomic status (SES) experience greater nicotine dependence, are less likely to quit smoking, and experience profound tobacco-related health disparities. There is an urgent need to improve upon evidence-based nicotine dependence treatments that are tailored for low-SES smokers. Mindfulness training increases rates of smoking abstinence and lapse recovery, but in-person mindfulness treatment is not easily accessible to low-SES smokers. Mobile health technology (mHealth) is an accessible, cost-effective modality for offering vital 24/7 smoking cessation support. We developed a text messaging program (iQuit Mindfully 1.0) that provides personalized, interactive mHealth messages to encourage low-SES smokers to use mindfulness and other smoking cessation techniques in the moments when they need them most. This program was designed based on iterative feedback from low-SES smokers, and serves as an adjunct to in-person mindfulness training. Our pilot work demonstrates that iQuit Mindfully 1.0 is feasible, acceptable, and perhaps most effective for low-SES smokers (i.e., 23.1% of participants living in poverty who received iQuit Mindfully achieved abstinence at end of treatment and 1-month follow-up, while none of those living in poverty quit in the in-person-only treatment). However, accessibility would be immensely improved by fully delivering the program through mHealth. This proposal aims to develop, refine and evaluate feasibility of iQuit Mindfully 2.0 (i.e., iQuit Mindfully that is fully delivered through an mHealth app to increase accessibility for low-SES smokers). Aims are: 1) Develop iQuit Mindfully 2.0 using an existing mHealth app platform to deliver mindfulness-based smoking cessation treatment that is specifically designed for low-SES smokers; 2) Refine iQuit Mindfully 2.0 based on usability testing with low-SES smokers; and 3) Evaluate the feasibility and acceptability of iQuit Mindfully 2.0. The app will be refined after 2 weeks of preliminary testing with 20 low-SES smokers. Then, 60 low-SES smokers will be randomly assigned to iQuit Mindfully 2.0 (n=30) or the NCI QuitGuide app (n=30) in a feasibility trial. Participants will complete questionnaire measures and biochemical confirmation of smoking behavior at baseline, 8, and 12 weeks; weekly assessments of hypothesized psychosocial mechanisms; and individual in-depth interviews at 12 weeks. The expected products of this feasibility study are: 1) engagement with the app and follow-up rates; 2) participant ratings and suggestions for further improvement; and 3) documented trends over time by condition in smoking status and hypothesized psychosocial mechanisms. Pending feasibility, this study would provide the groundwork for rapid launch of a full-scale randomized clinical trial to examine efficacy. If efficacious, the iQuit Mindfully app could provide more cost-effective, accessible smoking cessation treatment (e.g., offered at no cost through federally qualified health centers, substance abuse/mental health treatment/community centers, etc.) to target health disparities among low-SES smokers.